Desulfurization and sweetening of virgin distillates with an aldehyde



iatented Sept. 11', 1951 DESULFURIZATION AND SWEETENING OF VIRGIN DISTILLATES -WITH AN ALDE- HYDE Erving Arundale, Westfield, N.

Juterbock, Staten Island, N.

J and Edwin E. Y., assignors to Standard Oil Development Company, a corporation of Delaware Application January 27, 1949, Serial No. 73,106 9 Claims. (01. 19631) The present invention is concerned with an improved process for the production of high quality petroleum products. The invention is more particularly concerned with the treatment of virgin stocks especially those fractions boiling in the motor fuel boiling range. In accordance with the present invention mercaptans and other compounds of sulfur are effectively removed from sour petroleum fractions by treatment with a relatively dilute acid, preferably sulfuric acid, in conjunction with an aldehyde, as for example, formaldehyde.

In the manufacture of high quality petroleum products various procedures have been utilized in order to remove objectionable compounds of sulfur. In the refining of petroleum fractions boiling inthe motor fuel boiling range one conventional procedure employed is to contact the fraction with concentrated sulfuric acid. If the concentration of the sulfur compounds is relatively high, it is necessary to employ a relatively heavy acid treat. After treating, it is necessary to remove strong acids from the acid treated oil, for example by water-washing and caustic neutralization, and then to redistill and sweeten. This last process being the conversion of mercaptans still present to relatively innocuous disulfides.

It has now been discovered that the sulfur content of petroleum fractions, especially virgin petroleum fractions boiling in the motor fuel boiling range, can be reduced and the fraction sweetened by treating the sam with a relatively dilute acid, preferably sulfuric acid, in the presence of a small concentration of an aldehyde, preferably formaldehyde. I

The process of the present invention may be more readily understood by reference to the drawing illustrating one embodiment of the same.

Referring specifically to the drawing, a feed oil which for the purpose of illustration is assumed to be a crude petroleum oil is introduced into distillation zone In by means of feed line I. Distillation zone l may comprise any number and arrangement of distillation stages. Temperature and pressure conditions are adjusted in distillation zone III to remove overhead by means of line 2, hydrocarbon constituents boiling below the motor fuel boiling range. Hydrocarbon constituents boiling within the motor fuel boiling range are removed from zone [0 by means of line 3. Higher boiling fractions as for example, kerosenes, diesel fuel fractions and still higher boilin fractions are removed from zone III by means of lines 4, 5 and 6 respectively.

, gates.

In accordance with conventional practice the hydrocarbon fraction boiling in the motor fuel boiling range is condensed and passed into a storage zone 20. This fraction is removed from storage zone 20 by means of line I and usually contacted with concentrated sulfuric acid which is introduced into line 1 by means of line 8. Satisfactory mixing is secured by orifice mixing device 9 or equivalent means. The acid-oil mixture is introduced into zone 30 wherein a spent acid phase containing sulfur compounds segre- This acid phase is withdrawn from zone 30 by means of line H while the treated oil is withdrawn from zone 30 by means of line l2 and combined with a water wash which is introduced into the system by means of line l3. Mixing is secured by orifice mixer 33 or an equivalent device. The oil and water are introduced into zone 4|], wherein a water phase separates, which phase is withdrawn from zone 40 by means of line it.

The water-washedbil phase is withdrawn from zone 40 by means of line l5 and combined with an alkali, usually a dilute sodium hydroxide solution which is introduced into line I5 by means of line It. This mixture is introduced into zone 50 wherein a spent caustic phase separates which is withdrawn from zone 50 by means of line 36.

The treated oil phase is removed from zone 50 by means of line I! and introduced into distillation zone which may comprise any number and arrangement of suitable distillation stages. Temperature and pressure conditions are adapted in I zone W to remove overhead by means of line l8, hydrocarbon constituents boiling in the motor fuel boiling range. Hydrocarbon constituents boiling above the motor fuel boiling range are removed by means of line is and handled in any manner desired. The hydrocarbon stream removed overhead by means of line i8 is condensed in zone 2| and passed to a doctor sweetening, zone 10 by means of line 22. Here the hydrocarbon fraction is contacted with the conventional "doctor solution comprising lead oxide dissolved in an aqueous caustic soda solution. Free sulfur is introduced also. A gasoline fraction of satisfactory quality is withdrawn from zone 10 by means of line 23 and handled as desired. Other hydrocarbon fractions not boiling within the gasoline boiling range are handled similarly.

In accordance with the present invention, a relatively diulte acid, preferably sulfuric acid is employed rather than the concentrated sulfuric acid conventionally employed. Also an aldehyde, preferably formaldehyde is utilized. In accordance with the adaption of the present invention 3 formaldehyde is introduced into the oil stream by means of line 24. The oil and the formaldehyde are mixed in mixing device 25 or equivalent means. A diulte acid is introduced into the for- 4 washed and filtered. The results of the operations are as follows: (Formaldehyde concentrations expressed as weight per cent based on naphtha.)

Table I Higher Boil- Ma t ial Per cent er Operation Treatment v0]- Total Doctor Test 1 gg Per Cent on Feed 1 Naphtha processed as described except no acid treatment. 1. 8 0. 113 Did not pass. 48 0.7 vol per cent 88% H280 alone (=5#/b 1. 6 0. 044 do 0 1.58 vol per cent 88% H1804 alone 2, 6 1 0.79 vol per cent 88% E180; +0.5 wt. per cent Pa 1. 6 0

0.79 vol. per cent 88% H1804 +1.0 wt. per cent Pnra- 4 0 form. 0.79 vol. per cent 88% R1804 +0.5 wt. per cent CHrO 2. 0 0

(as formali 1 0.719 l:01d per cent 86% H2804 +0.5 wt. per cent acetal- 1. 7 0

e y e.

1.58% vol. per cent 88% H2801 +0.5 wt. per cent CH=O 1. 8 o

(as formalin). 1.58% vol. per cent 88% H1801 +1.0 wt. per cent OHIO 1. 8 0

(as formalin).

1 Material boiling above 250 F.

I The doctor test is a means of making sure that hydrocarbon fractions are free of mercaptans which render the fraction A sample of the hydrocarbon is shaken with a sodium plumhite solution and a trace of free sulfur.

lfaftcr slluk ing, the hydrocarbon, plumhite solution, and sulfur have not changed color, mercaptans are absent. the stock is swect doctor test is lass."

If discoloration occurs mercaptans are present and the test does not pass (l).\ P)

1 The copper number is the milligrams of mercaptan sulfur present in 100 ml. of sample under test which will react with a standard copper ammonium sulphate solution.

4 laraformaldehyde-the solid polymer of formaldehyde.

l 37% solution of formaldehyde in water.

maldehyde-oil stream by means of line 8 as heretofore described. When operating in this manner the condensed overhead stream from zone 60 comprises a satisfactory motor fuel and is removed from the system by means of line 26 and handled as desired. The present process will enable the by-passing of the doctor treating" operation.

The present invention may be more fully un-.

derstood by references to the following examples illustrating embodiments -of the same.

EXAMPLE 1 Various operations were conducted employing light prime cut naphthas secured from a West Texas crude. The naphthas had an Engler boiling test.

EXAMPLE 2 Additional operations were conducted using identical feed stocks and identical operating conditions except that the time of contact was 30 minutes. Smaller quantities of formaldehyde were also employed. The results of these operations are as follows:

Table II Per Cent Total Sulfur After Rerunning 553" Treatment Before After Copper Doctor Rerunning Rerunning No. Test Untreated naphtha rerun to 250 F. E. P 0.152 0.10 49 DNl. 0.79 vol. per cent 88% H2807 alone 0, 073 0. 033 8 DNl'. 0.781;?? cent 88% HzS04+U.025 wt. per cent 0.098 0.030 14 DN P.

1 0.7(i3lfi'cg per cent 88% HzS04+0.05 wt. per cent 0.005 0.035 14 DN P.

z 0.7'(1)Hv )l. per cent 88% HzSO4+0.l0 wt. per cent 0.005 0.033 12 BN1.

2 ofllflwg per cent 88% HzS0|+0.20 wt. per cent 0.050 0.020 0 Passed.

z OJgHWBL per cent 88% H1s0|+0.30 wt. per cent 0.085 0. 010 0 Do.

2 0.79 vol. per cent 88% H1S0+0.5 wt. per cent CHaO 2. 0. 109 0. 021 0 Do.

1 As 37% formalin solution.

It can be seen that the addition of as little as 0.2 weight per cent of formaldehyde to the acid results in a definite reduction in sulfur and mercaptan content and in a stock that will be sweet.

EXAIVIPLE 3 Additional operations were conducted in the manner as described with respect to Examples 1 and 2. The acid layer was separated and'the naphtha washed with water, neutralized with a 345% caustic soda solution. and rerun to an end point of 250 F. The results of these operations are as follows: (Formaldehyde added as 37% formalin solution unless stated otherwise.)

treated should have a bromine number not great er than about cg. Br./gm. The petroleum fraction treated may be washed when necessary with dilute alkali hydroxide solution before treator formaldehyde are effective treating agents when used alone. The use of the sulfuric acid and formaldehyde together produces the desired sweetening and sulfur reduction.

EXAMPLE4 A heating oil fraction boiling in the range from 375 F. to 650 F. and secured from West Texas crude was treated as indicated below for hour at about 70 F. Theoil was separated from the acid, water washed, contacted with a 3% caustic solution, and then rerun to an end point of 630 F. The distillate was water washed and filtered.

The results are as follows:

OHIO used as 37% Formalin solution. 1 Material boiling above 630 F.

The above results can be further improved by raising the contact temperature or by increasing the acid catalyst strength.

It was noted also that with the acid alone (second experiment) the sludge was shown to separate slowly whereas in the third experiment, it separated rapidly. 4

The present invention is generally concerned with the treatment of uncracked or virgin petroleum fractions boiling below about 700 F. These fractions are for example, diesel fuels, heating oils, kerosenes, gasolenes, light napthas and the like. The invention is particularly adapted to the refining of motor fuels which fractions boil below about 420 F.

It is preferred that the hydrocarbon fraction Table III 0 ng Treatment l Mama" l o t l ff Vol. Per Bum" 0. Test Cent on Untreated N apbtha Rerun 1.6 0. 105 49 DN P. 0.70 vol. per cent 88% H2804 alone 30 1. 0 0. 030 8 DNP. 1.58 vol. per cent 88 H1804 alone 30 2. 4 0. 027 2 DNP, 0.79 vol. per cent 88 H|S04+0.05 wt. per cent CH:0.- 30 2. 6 0. 035 14 DN P. 0.79 vol. per cent 88 a HzSO4+0.l0 wt. per cent CHg0. 30 2. 0 0. 035- 12 DN P. 0.79 vol. per cent 88% H=SO4+0.20 wt. per cent CHrO 30 2. 4 0. 020 0 Passed 0.70 vol. per cent 88'? H1S04+0.50 wt. per cent 01110.. 30 2. 2 0. 21 0 Do. 0.79 vol. r cent 88 0 H:S04+0.50 wt. per cent Para- 45 1. 6 0.013 0 Do.

formal ehyde. 0.79 oldper cent 88% H:S0|+0.50 wt. per cent Acetal- 45 1. 7 0. 016 0 Do.

c y e. 0.79 :01. per cent 88% H:SO4+0.2 wt. per cent 011:0- 30 0. 097 0 Do.

no rerun. 0.79 vol. per cent 88 HgS04+0.2 wt per cent CHaO..- 2. 5 2. 4 0. 034 1 DNP. 0.79 vol. per cent a H1SO4+0.2 wt. per cent OHIO 30 3. l 0. 034 1 DN P. 0.79 vol. per cent 60% H1S04+0.2 wt. per cent C1110 30 2. 5 0. 073 17 DNP. I 0.3 wt. er cent CH:0 alone no acid 30 2. 2 0.069 27 DN P.

1 Material boiling above 250 F. K 1 Acid cone. in acid-Formalin aqueous phase=75 wt. per cent. 1 Acid conc. in'acid-Formalin aqueous pbase=64 wt. per cent. Acid cone. in acid-Formalin aqueous phase=50 wt. percent.

It can be seen that neither 88 sulfuric acid 0 ment in order to remove hydrogen sulfide which may be dissolved therein.-

The preferred aldehyde comprises formaldehyde which may be used as a 37 wt. formalin solution. Other sources of formaldehyde such as, paraformaldehyde, trioxane, hexamethylene tetramine,-methylal or compounds liberating formaldehyde in the presence of acids can be used. Higher aldehydes (e. g. acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, acrolein,

etc.) can also be used-but in most cases the latter must be employed in slightly higher concentrations than iormaldehyde.-

Various acids of sulfur can be used as weal as acids of phosphorus, as for example, sulfuric acid, sulfonic acids and phosphoric acid. The preferred acid, however comprises sulfuric acid having a concentration in the range from 50 to 90 and preferably (55-80% in the aqueous phase of the acid-aldehyde mixture. The temperature of treatment should be in the range from about 20 C. to about'60 C. The time of contact will vary appreciably generally in the range from about 1 minute to 45 minutes. A preferred time of contact is in the range from 2-30 minutes. The amount of acid catalyst solution employed should be in the range from about 0.25 to 5 volume percent based upon the virgin distillate and preferably 0.5-2.0 volume percent. This volume includes the volume of acid added plus the volume of water, if any, entering with the aldehyde.

The amount of aldehyde employed should be in the rangefrom about 0.05 to 1% by weight based upon the distillate and usually below 0.5 weight percent. The amount of aldehyde necessary and also the acid concentration, contact time, and temperature will depend on the sulfur content, mercaptan content, and unsaturation, if any, of the distillate, its boiling range, and on the type of aldehydeemployed. Rerunning of the treated stock is not always necessary in order to obtain sweetening unless maximum sulfur reduction is desired.

As indicated, a particularly desirable aqueous solution comprises formalin (37% formaldehyde in water). However, it is to be understood that with respect to the present invention, if an aqueous carrier be employed for the aldehyde, the concentration of the added acid must be adjusted accordingly since the acid concentrations specifie'd are defined with respect to the total water present in the treating zone irrespective as to whether the water is introduced with the acid, or aldehyde or from other sources.

Having described the invention, it is claimed:

1. Process for the removal of objectionable sulfur compounds from virgin naptha containing the same which comprises treating said oil with a reagent consisting of 0.05 to 0.5% by weight, based upon the oil, of an aldehyde selected from the group consisting of formaldehyde and metaldehyde and with sulfuric acid in such amount that the concentration of the acid is in the range from about 50 to 88% in the aqueous phase of the mixture.

2. Process as defined by claim 1, wherein the concentration of the sulfuric acid is in the range from about 65 to 80%.

3. Process as defined by claim 1 wherein sai aldehyde comprises formaldehyde.

4. Process as defined by claim 1 wherein the amount of acid employed is in the range from 0.25 volume to 5 volumes per volum of oil being contacted.

5. Process for the removal of sulfur compounds from virgin petroleum oils boiling below about 700 R, which comprises treating said oils with a reagent consisting of sulfuric acid havin a concentration in the range from about 50 to 80% and with about 0.05 to 0.5% by weight, based upon upon the oil, of an aldehyde selected from th group consisting of formaldehyde and acetaldehyde, thereafter separating a spent acid phase, and removing a treated oil substantially free of sulfur compounds.

6. Process for the removal of objectionable sulfur compounds from virgin distillates boiling in the motor fuel boiling range which comprises treating said oil with a reagent consisting of an aldehyde and sulfuric acid, said aldehyde being selected from the group consisting of formaldehyde and acetaldehyde and being employed in a concentration of from about 0.05 to 0.5% by weight based upon the oil and said sulfuric acid having a concentration in the range from about to 88% in the aqueous phase of the mixture, removing a spent acid phase, thereafter water washing the acid treated oil followed by rerunning to produce a finished petroleum oil substantially completely free of objectionable sulfur REFERENCES CITED The following references are of record'ln the file of this patent:

UNITED STATES PATENTS Number Name Date 1,827,538 Nastukofi Oct. 13. 1931 2,011,199 Pelc Aug. 1'7, 1934 2.018,715 Fulton Oct. 29, 1935 2,068,850 Ellis Jan. 26, 1937 2,080,732 Morrell May 18, 1937 OTHER REFERENCES Gurwitsch, Principles of Pet. Tech. (new ed.), 1932, pages 104 to 108.

Ormandy et al., J. I. P. T. 10, pages 99 and 100 (1924). 

1. PROCESS FOR THE REMOVAL OF OBJECTIONABLE SULFUR COMPOUNDS FROM VIRGIN NAPTHA CONTAINING THE SAME WHICH COMPRISES TREATING SAID OIL WITH A REAGENT CONSISTING OF 0.05 TO 0.5% BY WEIGHT, BASED UPON THE OIL, OF AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE AND ACETALDEHYDE AND WITH SULFURIC ACID IN SUCH AMOUNT THAT THE CONCENTRATION OF THE ACID IS IN THE RANGE FROM ABOUT 50 TO 88% IN THE AQUEOUS PHASE OF THE MIXTURE. 